Deciphering the role of IspD (2‑C‑methyl‑D‑erythritol 4‑phosphate cytidyltransferase) enzyme as a potential therapeutic drug target against Plasmodium vivax

Abstract

Biosynthesis of isoprenoids (MEP Pathway) in apicoplast has an important role during the erythrocytic stages of Plasmodium, as it is the sole pathway to provide the major isoprene units required as metabolic precursor for various housekeeping activities. With the intensifying need to identify a novel therapeutic drug target against Plasmodium, the MEP pathway and its components are considered as potential therapeutic targets, due to the difference in the isoprenoid synthesis route (MVA) functional in the host cells. While few major components have already been studied from this pathway for their potential as a drug target, IspD (2-C-methyl-D-erythritol-4-phosphate cytidyltransferase) enzyme, the enzyme catalyzing the third step of the pathway has only been tested against a synthetic compound from Malaria box called MMV008138, which also has not shown adequate inhibitory activity against P. vivax IspD. In the present study, to validate the potential of PvIspD as a drug target, various antimicrobial agents were screened for their inhibition possibilities, using in-vitro High Throughput Screening (HTS) technique. Shortlisted antimicrobial drug molecules like Cefepime, Tunicamycin and Rifampicin were further validated by in-vitro biochemical enzyme inhibition assays where they showed activity at nanomolar concentrations suggesting them or their derivatives as prospective future antimalarials. This study also confirmed the in-vivo expression of PvIspD protein during asexual stages by sub-cellular localization in apicoplast and explores the importance of the IspD enzyme in the development of new therapeutics.

Keywords: 2-C-methyl-d-erythritol 4-phosphate cytidyltransferase (IspD); Apicoplast; Cytidine 5′-triphosphate (CTP); Methyl erythritol phosphate (MEP).